The formation and harvesting of sunflower seeds (i.e. Helianthus annuus seeds) is recognized to be an important industry of considerable economic impact in various sectors of the world. For instance, it is estimated that annually in excess of two million acres presently are commercially being planted in sunflower plants throughout the United States of America. Additionally, existing trends point to the increased growing of sunflowers as a source of both oil and food. See, "The Sunflower" by Charles B. Heiser, Jr., published by the University of Oklahoma Press (1976)
The sunflower plant has not escaped study by plant scientists over the years. It possesses perfect flowers which possess both male and female elements and in theory can undergo either self-fertilization or cross-fertilization. It further is well recognized that the sunflower blossom is composed of many individual florets (e.g. 500 to 1,000 florets arranged side by side as a disk) which must be individually pollinated if each is to result in the formation of a sunflower achene which includes a kernel. Since the kernel serves as the source of food for men and livestock, as well as the source of sunflower oil, such pollination is essential and of prime importance.
Naturally occurring sunflower plants found in nature are recognized to possess a high degree of physiological or sporophytic self-incompatibility (i.e. they are self-unfruitful) and accordingly commonly undergo at most only a slight degree of self-fertilization. The bulk of the fertilization which occurs in such sunflower plants must accordingly be the result of pollen derived from other sunflower plants growing in the same general area which is primarily transferred by insect vectors. See Page Nos. 18 and 19 of the Heiser treatise. Since normally occurring insect populations are commonly incapable of servicing literally billions of individual florets in a growing area where such sunflower plants are growing in large numbers, the resulting seed set commonly is poor among large concentrations of sunflower plants growing in nature.
It additionally is recognized that the longevity of sunflower pollen is influenced by the environment it encounters following dehiscence. For instance, if the days are hot (e.g. 100.degree. F.) and the relative humidity low (e.g. 20 percent or less) the pollen may live for only a few hours at most once it is exposed to the environment. However, when the temperature is lower (e.g. 70.degree. to 75.degree. F.) and the relative humidity is higher (e.g. 40 to 45 percent), the sunflower pollen may live for several days (e.g. up to three days). There accordingly is recognized to be a finite period of time in which sunflower pollen can satisfactorily carry out its intended function.
Over the years the research of sunflower breeders has resulted in the development of sunflower cultivars which are agronomically improved over those sunflowers commonly found growing in nature. For instance, some cultivars commonly are capable of undergoing a greater degree of self-pollination assuming advantageous growing conditions are encountered. At least some of the physiological self-incompatibility is overcome in such cultivars and it is possible for the stigma to curve around and to eventually contact its own pollen and accomplish fertilization assuming it has not already been killed due to adverse environmental conditions. However, even under the most advantageous environmental conditions such self-fertilization is still limited and falls far short of accomplishing pollination of all the individual florets encountered in a commercial growing area where such plants are grown.
Other researchers have taken a different approach and have attempted to develop a technique for producing seeds capable of forming F.sub.1 hybrid sunflower plants which relies largely upon the use of self-incompatible sunflower plants as seed parents so that self-pollination is impossible. Such technique, however, required the substantial utilization of insect vectors, and posed an insurmountable problem for the F.sub.1 hybrid sunflower seed producer when he attempted to maintain the largely self-incompatible seed parent line on a commercially practicable basis. Such approach has not been a commercial reality.
In more recent years cytoplasmic male sterile sunflower plants have been discovered as well as maintainer sunflower plants for the same which has made possible the production of other synthetic F.sub.1 hybrid sunflower cultivars which presently are being commercially marketed for use by sunflower growers in the United States. Such cultivars constitute a significant advance in the production of sunflower plants since they offer the grower the prospect of obtaining hybrid vigor in his crop. There, nevertheless, still have remained significant shortcomings in this approach. For instance, pollen transfer by insect vectors still is essential both in the production of the hybrid sunflower seed and when grown by the farmer if adequate seed formation is to be achieved. The sunflower grower commonly will not have available the required insect population to accomplish efficient pollen transfer. He accordingly is at the mercy of the local insect population and the weather which influences the longevity of the pollen awaiting transfer by the insects. A high degree of pollen transfer is largely impossible unless high concentrations of insect vectors can saturate the area, and the weather conditions are such that the life of the pollen from the pollinator is not unduly attentuated. Factors having a significant economic impact are to a large extent outside the control of the grower.
Others have proposed that the development of sunflower cultivars having shorter anthers might possibly make it easier for bees or other insects to forage for pollen and nectar within the sunflower blossom and thereby aid in raising the level of cross-pollination. Such an approach has not been a commercial reality.
Additionally, commercial sunflower growers commonly have had to cope with another problem in the form of the sunflower head moth (i.e. Homeosoma ellectelum) which deleteriously influences the sunflower seed harvest. Such insects if unchecked can destroy the sunflower blossom and the desired crop of sunflower seeds. Accordingly, it has been necessary to treat the sunflower blossoms with an insecticide to control this harmful insect. However, the timely application of an insecticide to limit the damage done by this insect pest also results in the destruction of other desirable insect vectors (e.g. honey bees) which are required in great numbers if pollen is to be transferred to the sunflowers to accomplish seed set.
It is an object of the present invention to provide an improved process for the production of sunflower seeds.
It is an object of the present invention to provide a process for the production of sunflower seeds in increased yields thereby offering the sunflower grower a significant economic advantage.
It is an object of the present invention to provide a process for the production of sunflower seeds wherein the pollination of each floret of the sunflower blossom is facilitated thereby resulting in an enhanced seed formation.
It is an object of the present invention to provide an improved sunflower seed product which can be utilized by a sunflower grower to more reliably accomplish the pollination required for sunflower seed production without the necessity of relying upon pollen-carrying insect vectors.
It is an object of the present invention to provide an improved process for the production of sunflower seeds which are capable of growing F.sub.1 hybrid sunflower plants.
It is an object of the present invention to provide an improved process for the production of sunflower seeds which is capable of maintaining an inbred sunflower line on a more efficient basis.
It is another object of the present invention to provide a process for the production of sunflower seeds which in at least some embodiments is not adversely influenced by the treatment of the sunflower blossoms with an insecticide.
It is a further object of the present invention to provide a process for the production of sunflower seeds in increased yields which is capable of accomplishing a satisfactory level of pollination even if following pollen dehiscence the florets are subjected to thunder showers and/or sprinkler irrigation which would normally result in pollen loss.
These and other objects, as well as the scope, nature, and utilization of the invention will be apparent from the following detailed description and appended claims.